The use of glycol ethers, especially ethylene glycol mono butyl ethers (EGMBE), has come under increased pressure from a health, safety and environment (HSE) perspective. EGMBE is a suspected carcinogen for humans, causes hemolysis, is under strict scrutiny in California, and is being phased out in Canada. With full disclosure rules for oil and gas chemicals being adopted for hydraulic fracturing fluids in most oil producing states jurisdictions, there is an increased urgency to have greener solvents in formulations. Oil and gas service companies are looking for viable alternatives which provide good performance and HSE profile. Some solvents have been used instead of EGMBE; however, many such solvents suffer the same drawbacks as EGMBE, such as being environmentally unfriendly or similarly toxic and hazardous. These are other glycol ethers like PnB (propylene glycol n-butyl ether), butyl carbitol (diethylene glycol butyl ether), ethylene glycol monoacetate, triethylene glycol monoethyl ether, 1,1′-oxybis(2-propanol), triethylene glycol monomethyl ether, triglyme and diglyme, which were reported more often than many “priority pollutants”.
Glycol ethers are commonly used as activator solvents in guar gum-mineral oil slurries (“guar slurries”). Guar slurries are dispersions of dry guar particles in mineral oil with hydrophobically modified clay as the suspending aid. Glycol ether solvents, e.g., ethylene glycol mono butyl ether (EGMBE), are conventionally added as activator solvents for the clay. Such activator solvents break up the galleries to disperse the clay platelets in mineral oil (i.e., “activates” the clay). As used herein, the term “activator solvent” means a compound which is added to the suspension composition to assist the clay component therein to develop viscosity. The activated clay serves to thicken (i.e., increase viscosity of) the carrier, generally mineral oil, or to form a weak gel or pre-gel to help suspend the guar particles and make a stable slurry. The carrier can also include polyethers, esters, higher alcohols, or vegetable oils, aside from mineral oil, as well as mixtures thereof. Stable slurries where the guar or polysaccharide particles remain suspended for a sufficient period of time are important in application for storage and transport. If the particles settle and hard pack as a sediment, the slurry becomes hard to handle and difficult to pump or pour out of drums in the field. In some conventional embodiments the slurries contain a small amount of surfactant and/or acid components to help with the hydration of the slurries. Such additional components can also have an impact on the viscosity of the slurry to facilitate handling.